1. Field of the Invention
This invention relates to clean-burning fragrance candles with a consistent flame size and burn rate. Furthermore, this invention relates to wax compositions used in the candles, methods of manufacturing the candles, and the manufacture of the wax compositions used in the candles.
2. Description of Related Art
Fragrance-emitting candles are widely available and are typically employed to impart odorant into a space. Generally, the odorant will mask other odors, or simply impart its own, in order to make a space more pleasant.
Early fragranced candles included mixtures of wax, odorant, and optional additives, such as colorant. Such candles were generally manufactured by cooling a molten wax composition, typically containing paraffin, around a candle wick. The solidified wax composition, at a microscopic level, includes wax crystals packed against each other. Components of a wax composition, such as colorant, are typically trapped in the inter-crystal spaces. Fragrance molecules, however, are typically too small to be held in these inter-crystal spaces. Consequently, in early fragrance candles, the fragrance molecules often diffused through the candle while the candle was in solid form. This diffusion eventually brought the fragrance molecules to the surface, leading to weeping, even when the candle was lit. In addition to the loss of fragrance, weeping gave a wet, greasy, feel to the candles.
The problem of weeping was eventually brought under control by the addition of chemicals that reduce the crystal size in the solidified candle wax. The smaller crystals pack tightly enough to trap the odorant inside their inter-crystal spaces.
Typically, microwax or large olefinic materials are mixed with the main wax composition to keep the crystal size, and the inter-crystal spaces, smaller. Generally, microwax is the product remaining after vacuum distillation of crude oil products at high temperatures and reduced pressure to isolate a target product. The target product is usually paraffin wax, the main wax content of candles. Such leftover products forming the microwax may include larger paraffins. Olefinic materials, in the form of alkanes, may be obtained from a variety of sources, such as the petroleum industry, and typical sizes for these alkenes includes those with ten or more carbon atoms.
While the use of microwax and olefinic materials (referred to collectively as “microwax” herein) is beneficial in reducing fragrance loss in candle waxes, there are negative affects imparted to candles employing these compounds, including, for instance, (i) higher processing temperatures, (ii) coking, (iii) carbon deposits, and (iv) inconsistent flame sizes and burn rates.
The processing temperatures are generally higher because microwax has higher melting temperatures than the main wax utilized in candle compositions (typically paraffin wax of smaller sizes than microwax).
Coking and carbon deposits left by candles employing microwax result from incomplete combustion of the microwax used. These materials often do not burn completely because they are very large and tend to only partially oxidize, thereby yielding smoke and coking the candle surface.
The flame size and burn rates among different candles, and even for an individual candle over its life, employing microwax may be inconsistent. There are two main reasons for these inconsistencies. First, the source of the microwax or olefinic product may vary from batch to batch, because the inconsistent composition of crude oil product yields varying microwax or olefinic compositions. This variability may cause otherwise similar candles to burn differently. Second, these materials often do not completely mix with the balance of the candle wax composition, yeilding areas with different concentrations of these compounds. This non-homogeneity causes flame size and burn rate to vary, even with respect to an individual candle over time.
Ethylene vinyl acetates (“EVAs”) have been used as a partial substitute for microwax in fragranced candles, to lessen the problems associated with these materials. U.S. Pat. No. 4,110,261 discusses the use of EVAs, in general, in candle wax compositions. This patent is hereby incorporated by reference in its entirety. EVAs are known to make the crystal size smaller as well as assisting in making such candles release from manufacturing molds easier. EVAs also are known to make candles more opaque. However, because EVAs may cause similar smoking and coking, undesirable characteristics are still present in such candles employing EVAs as a partial substitute for or addative to the microwax. In addition, we have found that, when EVAs are used as a complete substitute for microwax, smoking and residues may become higher than in the case of olefinic or microwax-containing candles.
High molecular weight alcohols (“HMWAs”) are known to make candle flames more luminous and white. The use of these alcohols has been partially disclosed in U.S. Pat. No. 1,950,814, which is hereby incorporated by reference in its entirety. However, HMWAs have not been used a substitute for microwax inasmuch as they alone do not impart the ability to retain fragrance within the wax.
We have found that a combination of such alcohols with EVAs may be used as a substitute for microwax in fragranced candle waxes, and that substitution of the combination results in candles with qualities superior to those of candles using microwax or olefinic materials. For example, such candles typically exhibit less smoke and coking, while producing a more consistent flame size and burn rate, all without the problem of weeping.